The proposed study is designed to use multiple anatomical techniques to investigate the organization of peptide systems in the vertebrate retina. These studies examine 1) the localization and synaptic organization of peptide systems, 2) the postsynaptic site of action of peptide systems and 3) the identities of those classical transmitted systems with which peptide systems interact at the pre- and post-synaptic level. Initial studies will be concentrated on the enkephalins (enk) in the chicken, larval tiger salamander and goldfish retinas. The specific objectives for the next three years include: 1) Immunocytochemistry will be utilized to examine at the light microscopic level the development of enk-amacrine cells in the chicken retina. 2) Immunocytochemistry will be used to look for the presence of other opioid peptides (e.g. Beta-endorphin) in the chicken, larval tiger salamander and goldfish retinas. 3) In the same retina, enk-immunocytochemistry will be combined with HRP-backfilling of ganglion cells from the optic tectum to determine 1) if enk-cells synapse onto ganglion cells and 2) if there exists enk-ganglion cells in the larval tiger salamander retina. 4) Autoradiography will be employed at the light microscopic level to determine the anatomical distribution of opiate receptors in the chicken retina. 5) In the chicken, larval tiger salamander and goldfish retinas a combination of enk-immunocytochemistry and transmitter uptake-autoradiography will be used to determine 1) at the light microscopic level, if enkephalin is co-localized with classical transmitters in the same cell and 2) at the electron microscopic level, if there exists direct synaptic interactions between enk- and classical transmitter-systems.